984 COPPER 



It is, however, tlio only method that has hitherto been profitably employed in the 

 Rio Tinto district. 



The produce of some of the mines of this district is under 1 per cent, About 2,500 

 tons of the richest of the ores produced by the mines in the Rio Tinto district, are 

 shipped from Huelva, a port near Seville, for England ; and the result has been that 

 a very large industry has been created. See PYBITES. 



The Process of extracting Copper from tfte Water that drains out of the Mine, at JKio 

 Tinto, called the ' System of Natural Cementation' (Precipitation). The mine worked 

 by the Spanish Government at Rio Tinto is formed in a mass of iron pyrites containing 

 copper ; and its immense labyrinth of excavations is known to extend over a length 

 of 600 yards and i -width of 100 yards (and prcbably to a much greater extent); 

 the earliest of -which workings must date back to very remote times ; for in the dif- 

 ferent excavations are still to be found the impressions of hands, evidently guided by 

 the science of the ancients, middle ages, and of more modern times. 



The sixth, or lowest level in the mine, where .all the operations of the present day 

 are carried on, is 80 yards deep (from the top of the hill in which the lode is found), 

 and it is from this level that the mine is (naturally) drained by an adit. From the 

 roof, at the extreme end of a gallery at this level, flows, from an unknown source, a 

 stream of water rich in copper, -which, together with the drainage from other points 

 of the mine, is directed through a channel to the adit ' San Roque,' that empties its 

 waters at the foot of the hill, where the copper is extracted. 



An able engineer has thus explained the phenomena of ' natural cementation : ' 

 ' The natural ventilation through the open excavations of this mine, combined with 

 the humidity of the ground, produces a natural decomposition of the materials com- 

 posing the lode or vein, and thereby forming sulphates of iron and copper, which the 

 water is continually dissolving and carrying off, thus forming the substance of this 

 " natural cementation.'" 



This said adit ' San Roque,' which empties its waters on the south side of the 

 hill, has placed in it two wooden launders, or channels, about 12 inches -wide and 

 15 inches deep, and (in the year 1853) 400 yards long; in the bottom of these 

 launders are placed pieces of pig iron, and to this iron adhere the particles of copper 

 which the slowly-flowing water contained in solution. In ten days the iron becomes 

 coated with copper, so pure as to be worth 80 per cent, for fine-copper, and so 

 strongly formed in scales as to resist to a certain extent the action of a file, and give 

 a strong metallic sound on being struck with a hammer. At the expiration of ten 

 days, or earlier, the scales of copper so formed on the iron are removed, that the surface 

 of the iron may be again exposed to the action of the mineral water ; and the process 

 repeated to the entire extinction of the iron. The copper thus obtained passes at once 

 to the refining furnace. 



Since 1853 it has been discovered that the water escaping from the launders in the 

 adit, 400 yards long, still contained copper, and they have been lengthened to nearly 

 1 ,000 yards with good effect. 



The production of copper by cementation is carried on not only at Rio Tinto, but 

 also at the Tharsis Mines in Spain, and at San Domiugos in Portugal. 



lAnz Copper Process. At Linz on the Rhine, and some other localities in Ger- 

 many, the poorer sulphides of copper, containing from 2 to 5 per cent, of that metal, 

 are treated by the following process : 



The ores coming directly from the mine, and without any preliminary dressing, 

 are first roasted in a double-soled furnace, and then taken to a series of tanks sunk in 

 the ground, and lined with basalt. These tanks are also provided with a double 

 bottom, likewise formed of basalt, so arranged as to make a sort of permeable dia- 

 phragm, and on this is placed the roasted ore, taking care that the coarser fragments 

 are charged first, whilst the finer particles are laid upon them. 



The cavity thus formed between the bottom of the tank and the diaphragm, or 

 false bottom, is connected, by means of proper flues, with a series of oblong retorts. 

 through each of which a current of air is made to pass from a ventilator, or a pair of 

 large bellows, set in motion by steam or water power. 



In order to use this apparatus, a quantity of ore is roasted in the reverberatory 

 furnace, and subsequently placed in the tanks, taking care that the first layer shall be 

 in a coarser state of division than those which succeed it. 



The retorts which are formed of fire tiles, and are about 6 inches in height by 1 foot 

 in width and 6 feet in length are now brought to a red heat, charged with blende, 

 and the blast applied. 



The sulphurous acid thus formed is forced by the draught through the flues, where 

 it becomes mixed with nitrous fumes, obtained from a mixture of nitrate of soda and 

 sulphuric acid, and ultimately passes into the chambers beneath the diaphragms on 

 which are laid the roasted ores, which must bo previously damped by the addition of a 



